Dyeing and printing textiles with vat dyes using reductones and/or reductonates

ABSTRACT

Process for dyeing and printing textile material with vat or sulfur dyes using reductones or reductonates at pH about 12 or more in the presence of a quinoid compound which is soluble in water in the said pH range, and dye formulations which contain reductones or reductonates as reducing agents. The reducing agents are resistant to atmospheric oxygen and do not cause any overreduction in the case of sensitive dyes.

United States Patent Baumgarte et al.

[ DYEING AND PRINTING TEXTILES WITH VAT DYES USING REDUCTONES AND/ORREDUCTONATES [75] lnventors: Ulrich Baumgarte; Siegfried Weigold, bothof Limburgerhof; Werner Scheuermann, Ludwigshafen, all of Germany [73]Assignee: Badische Anilin- & Soda-Fabrik Alttiengesellschaft,Ludwigshafen (Rhine), Germany [22] Filed: Dec. 20, 1972 [21] Appl. No.:316,865

[30] Foreign Application Priority Data Dec. 24, 1971 Germany 2164463[52] US. Cl. 8/34; 8/37; 8/70;

[51] Int. Cl D06p 1/24 [58] Field of Search 8/34, 37, 70, 88, 54.2

[56] References Cited UNITED STATES PATENTS 2,598,120 5/1952 Griffith8/34 X 3,122,409 2/1964 Bardt 8/34 1 151 May 13, 1975 3,454,347 7/l969Leimbacher 8/34 X 3,464,780 9/1969 Weber et al. 1. 8/34 3,758,272 9/1973Datye et al. 8/174 X OTHER PUBLICATIONS Kneicht et al., Principles &Practice of Textile Printing, Charles Grifiin & Co., Ltd., London,England, l952, Pp. 268 & 269.

Primary Examiner-Benjamin R. Padgett Assistant Examiner-P. A. NelsonAttorney, Agent, or Firm-Johnston, Keil, Thompson & Shurtleff [57]ABSTRACT Process for dyeing and printing textile material with vat orsulfur dyes using reductones or reductonates at pH about 12 or more inthe presence of a quinoid compound which is soluble in water in the saidpH range, and dye formulations which contain reductones or reductonatesas reducing agents. The reducing agents are resistant to atmosphericoxygen and do not cause any overreduction in the case of sensitive dyes.

12 Claims, No Drawings DYEING AND PRINTING TEXTILES WITH VAT DYES USINGREDUCTONES AND/OR REDUCTONATES The invention relates to the dyeing andprinting of textiles with vat dyes or sulfur dyes using reductonesand/or reductonates.

In the simplest case, reductones are enediols but in more general termsthey are compounds having a similar structure to enediols and which arederived from enediols by replacement of one or both of the hydroxylgroups by amino groups and/or sulfhydryl groups. Reductonates arecompounds which under the influence of sufficiently strong protonacceptors are converted into enediolate anions. Reductones andreductonates may therefore be represented by the general formula:

..o=== R x x in which X and X are identical or different and are OH, O

NH NHR and SH; R and R are identical or different and are H, alkyl,

hydroxyalkyl, for example CH OH, COOH, esterified COOH,

The enediol or enediolate grouping may form part of a ring system sothat R and R form together bridging members of the following type:

in which R" is alkyl or substituted alkyl such as -CHOHCH OH in the caseof ascorbic acid. The said grouping may also be part of an aromatic ringsystern, for example in the case of pyrocatechol or pyrogallol in whichthe bridging member is -CH=)\ CHCH=CH- or Examples of typical reductonesand reductonates are hydroxyacetone. dihydroxyacetone, glycol aldehyde,dihydroxybutanone, 2,3-dihydroxyacrylaldehyde known as triosereductone,ascorbic acid, cyclopen tenediolone known as reductic acid and the ethylester of a-amino-B-ketobutyric acid. Triosereductone and reductic acidare obtained by acid or alkaline degradation of saccharides orpolysaccharides such as glucose, starch, molasses and pectin.

Reductones and reductonates have already been used in printing with vatdyes but either unsatisfactory results have been achieved or a purposeother than reduction has been aimed at. Attempts have been made to usethe compounds as reducing agents together with sodium carbonate andsodium bicarbonate in textile printing. The results were not viablebecause of the inferior reductive effect. The results are alsounsatisfactory when the compounds are used together with caus tie sodasolution and borax. On the other hand the compounds have been used incombination with sodium dithionite (hydrosulfite) or sulfinic acidderivatives for example in order to avoid overreduction of sensitivedyes or to achieve stabilization of the system against atmosphericoxygen. The use of inorganic reducing agents has often met withcriticism recently because waste water problems may be encountered.

We have now found that textiles can be dyed and printed with vat dyes orsulfur dyes more advanta geously by using as reducing agent a reductoneand/or reductonate in a pH range of from l2 upward in the presence of aquinoid compound which is soluble in water in this pH range andpreferably an anthraquinone derivative.

Reductones and reductonates to be used in the process of this inventionare the compounds described above. Where the compounds do not exhibitthe said structure in the neutral range, they achieve it in the alkalinerange.

As may be seen from the above lists, the reductones and reductonates(hereinafter referred to as reducing agents for short) are mainlywhydroxycarbonyl compounds. For reasons of economy those reducing agentsare preferred which are readily accessible such as hy droxyacetone,triosereductone obtainable from the degradation of saccharicles orpolysaccharides or re ductic acid.

Examples of quinoid compounds are derivatives of benzoquinone,naphthoquinone, acenaphthenequinone or anthraquinone containingchlorine, hydroxy, carboxylic and/or sulfonic acid groups. for exampletetrachloro benzoquinone, l,4-naphthoquinone. 2,6- hydroxyanthraquinone,2,7-dihydroxyanthraquinone and l,4-dihydroxyanthraquinone, anthraquinonecarboxylic acids, anthraquinone sulfonic acids such asanthraquinone-2-sulfonic acid, anthraquinonelfi disulfonic acid,anthraquinone-2,7-disulfonic acid andl,4-diamino-anthraquinone2-sulfonic acid. Because of their action thesecompounds may also be termed reduction catalysts or accelerators.Mixtures of the said compounds may also be used.

The process of the invention may be carried out in the pH range fromabout l2 upward, but a pH of from 13 upward is preferred.

In addition to anthraquinonoid dyes, the cobalt phthalocyanines andindigoid dyes are included under vat dyes for the purposes of thepresent invention.

The reducing agent is generally used in an amount of at least by weightbased on l00% (pure) dye. About 0.1 to about l0%, preferably from about2 to about 5%, by weight based on reducing agent may be used asaccelerator. A larger excess of accelerator does not do any damage. Itshould be remembered that the said minimum amounts of reducing agent andaccelerator are only guiding values because they depend on theindividual dye, pH and concentration of the dye liquor, the dyeingtemperature and also the particular reducing agent and accelerator. Themost advantageous amounts may be ascertained by preliminary experimentby preparing for the chosen method test colorations under otherwiseconstant conditions with different re ducing agents and accelerators andevaluating the results. Measurements of vatting speeds understandardized conditions are also informative.

The reducing agents may be used in all conventional dyeing methods withvat dyes and sulfur dyes, i.e. in

dyeing from a dye liquor, for example in package and jigger dyeing. andin continuous methods, for example pad-steam methods.

In optimum procedures the vatting may take place at low temperatures,for example at room temperature. so that the dyeing temperature dependsonly on the affinity of the dye. For dyeing from a liquor it isconvenient to aim at the lowest possible final temperature so as toincrease the color yield; it may be necessary during dyeing to usehigher temperatures in order to produce level dyeingsv The said reducingagents permit the use of high dyeing temperatures of about lC and eventhose above 100C without complications (for example by overreduction Theprocess of this invention is also suitable for continuous dyeing methodswhich comprise applying the dye in pigmentary form to textile sheetmaterial, giving an intermediate drying, applying a chemical liquorcontaining reducing agent, developing at elevated temper atures. forexample in an atmosphere of steam at 100C, and finishing off.

Similar considerations apply to printing with vat dyes or sulfur dyes,for example printing the dye in a print paste containing a conventionalthickening agent, intermediate drying, applying a padding liquor containing a reducing agent and developing in a steamer suitable for two phaseprinting, finishing off being carried out conventionally by rinsing,oxidizing and soaping.

The usefulness of the reducing agents is not exhausted by thedescription of the procedures; rather the reducing agents also offer thepossibility of commercial forms not hitherto realizable. Thus forexample liquid dye formulations may be introduced into commerce whichcontain vat dye. reducing agent and accelerator and are adjusted to beacid or neutral. They remain stable until they are made alkalineimmediately prior to use. Dye pastes and powdered dyes which have beenadjusted to be acid or neutral may also be marketed which contain dye,solid reducing agent and accelera tor. if desired with dispersing agentand diluent.

The advantages of this invention. including those already describedabove, may be summarized as follows: high resistance of the reducingagent to atmospheric oxygen so that formulations can be produced whichhave a long shelf life; no undesirable reduction of the dye in acid orneutral medium; no overreduction of sensitive vat dyes. for example inthe case of an indanthrone derivative; some of the reducing agents areliquid and may therefore be dosed easily; the reducing agents are notelectrolytes in the proper sense and therefore do not offer any levelingproblems.

Since the reductones and reductonates and their oxidation productsformed in the liquor on vatting are biologically degradable these dyeliquors are more acceptable from an environmental point of view thanliquors which contain dithionite or oxidation products thereof formed invatting.

It is preferred to use caustic soda solution to achieve an alkalinerange; caustic potash solution is also suitable.

The following Examples illustrate the invention.

EXAMPLE 1 Rayon yarn on cheeses is treated in a commercial yarn-dyeingapparatus at a liquor ratio of :1 with a liquor of the followingcomposition:

l part of the dye C.l.Vat Green 1 (Colour Index (I956) No. 59825) partsof aqueous sodium hydroxide solution (38 Baume) 3 parts ofdihydroxyacetone 0.03 part of Z-hydroxyanthraquinone 955.97 parts ofwater 000.00 parts.

The temperature is raised from 25C and to 60C in IS minutes. Dyeing iscontinued for another 30 minutes at this temperature. Finishing off iscarried out as usual. A very level dyed cotton yarn is obtained which isnot inferior in color yield and fastness properties to con ventionaldyeings with hydrosulfite as reducing agent.

EXAMPLE 2 Unbleached cotton yarn on cheeses is treated on a commercialhigh temperature dyeing apparatus at a liquor ratio of l5zl at 20C witha liquor of the following composition:

The liquor is heated to ll5C within 30 minutes. Dyeing is continued foranother 45 minutes at l l5C, the liquor allowed to cool to C and thedyeing finished off in the usual manner. A level blue dyed material isobtained showing very good penetration and very good fastness propertieswithout any loss of dye by overreduction.

EXAMPLE 3 Cotton yarn on cheeses is dyed on a conventional dyeingapparatus at a liquor ratio of 101i at C with a liquor of the followingcomposition:

4 Parts of the dye ClVat Blue 4 (Colour Index (1956) No. 69800) 40 partsof aqueous sodium hydroxide solution (38 Baume) 8 parts of glucose 0.2part of 2 hydroxyanthraquinone 947.8 parts of water 1000.0 parts After adyeing time of 60 minutes the dyeing is finished off as usual. A textilematerial is obtained which shows good penetration without any loss ofdye occurring by overreduction.

EXAMPLE 4 Previously cleaned and bleached cotton poplin is padded at 25Cin a conventional two-roll padding machine with 50 parts of the dyeClVat Green I (Colour lndex {1965)N0. 59825) 950 parts of water 1000parts.

The impregnated cloth is then given an intermediate f u d Clv Y n P8115O a ye OW vat ye. erg at B OW dYl/mg a commuous mcihod at P a 1 (ColourIndex (I956) No. 70600) in the fonn ofa conventional two-roll paddingmangle at 25C with 20% aqueous paste l00 parts of water 600 parts of a3% decoction of carob bean flour 200 parts of a l0% wheat starch paste80 parts of aqueous sodium hydroxide solution (38 Be) W m 30 parts ofglucose solution (50%) pa 1 part of l 4-diaminoanthraquinone-2sulfonicacid 389 P of Wale After the cloth has been printed and dried it istreated 1000 parts with:

and steamed at 103C for 60 seconds in a continuous steamer and finallyfinished off as usual. A satisfactory 744 P of d bt d h. h t th dd 50parts of sodium hydroxide yeing is 0 mm w 1c 18 even a e en s an on 200pans of glucose (50%) both 5ide5 1 part of anthraquinone-Z-sulfonic acid5 parts of sodium tetraborate EXAMPLE 5 1000 P Bleached cotton yarn istreated on cheeses in a con ventional yarn-dyeing apparatus at a liquorratio of l5:l with a liquor of the following composition:

While still moist the cloth is exposed for thirty sec- 20 onds to anatmosphere of steam devoid of air and without superatmospheric pressureat 120C. To finish off the cloth it is treated for 2 minutes in runningwater at 2 parts f we dye CJ-vm Orange 3 20C and for 2 minutes in anaqueous solution contain- (C r Index 59300) ing 2 g of sodium perborateper liter which is at 95C.

' 0 40 $23 or aqueous sod'um hydrox'de 501mm (38 25 oxidized, soaped,rinsed and dried. A yellow print is ob- 3 parts of hydroxyacetone tamedon a Whlt ground. 20 parts of sodium sulfate (anhydrous) 0.06 part ofZ-hydroxyanthraquinone EXAMPLE 8 934.94 parts of water pans Bleachedcotton yarn on cheeses is dyed in a conventional dyeing apparatus at aliquor ratio of l0:l at 80C Dyeing is continued for 60 minutes at 24Cand the with a liquor of the following wmposition:

dyeing is then finished off as usual. A level satisfactory dyeing ISobta ned having good fastness at a color 10 Pam ofthe dye formulationdescribed below strength which is noticeably higher than in the usualvat 40 parts or aqueous sodium hydroxide solution (38 Be) dyeing by thelK-process. 22. Wale 1000 parts. EXAMPLE 6 Previously cleaned andbleached cotton twill is pad- The dye formulauon conslsts of:

ded at 25C in a conventional two-roll padding mangle 40 Wlth 20 parts ofthe dye C.l.Vat Blue 14 (Colour Index ([956) NO. 69810) 10 parts ofnaphthalenesulfonic acid condensed with formaldehyde 25 Fans of i; dye23: 2 40 parts of hydroxyacetone (Colour n ex (1 (ll part of2hydr0xyanthraquinone and 975 parts of water 9.9 parts of water. Theaqueous dispersion should 1000 parts. have a pH of from 4 to 5.

The liquor pickup should not exceed 80%. The dyeing After a dyeingperiod of 60 minutes the yarn is finis then steamed for 60 seconds at103C in a convenished off as usual. A brilliant blue dyeing is obtainedtional steamer which is fitted with a booster for the with an excellentcolor yield and very good fastness method known as the wet steam method.properties.

T t xtil material is treated in the booster with a f e e EXAMPLE 9solution of the following composition:

100 parts of aqueous sodium hydroxide solution 3 pans of the dye CINE!Blue 43 (Colour Index (38 Be) (1956) No. 53,630) is made into a pastewith 25 P of hydroxyacemne I 20 parts of an aqueous sodium hydroxidesolution P of zhydl'oxyamhraqumonc (38 Be) and after fifieen minutes isintroduced 3745 P of water into a solution at 70C, of 1000.0 parts. 6parts of glucose 003 part of 2,6-dihydroxyanthraquinone and 970.97 partsof water The dyeing is finished off as usual. A cloth showing W Pam verygood penetration is obtained with a high color yield.

Five minutes later cotton yarn on cheeses is dyed with 6 EXAMPLE 7 thisliquor in a conventional yarn-dyeing apparatus at A cotton cloth isprinted with the following print a liquor ratio of 10:1 at C. After adyeing period of paste: 60 minutes the yarn is finished off as usual. Ablue dyeing typical of this dye is obtained having good fastnessproperties.

EXAMPLE 10 Previously cleaned and bleached cotton cloth (basket weave)is padded at 25C in a two-roll padding machine with 25 parts of the dyeC.l.Vat Blue 6 (Colour Index I956) No. 69825) in 975 parts of water 1000parts.

80 parts of aqueous sodium hydroxide solution (38 Be) 14 parts ofhydroxyacetone l4 parts of chloranil (tetrachlorobenzoquinone) and 904.6pans of water [000.0 parts.

The impregnated cloth is steamed for 60 seconds at 103C in saturatedsteam in a steamer and then finished off as usual.

A satisfactory blue dyeing is obtained whose depth of color is clearlygreater than that of a dyeing which has been prepared in the absence ofchloranil.

We claim:

1. A process of dyeing or printing cellulose textiles with vat dyes in apH range from about 12 upward wherein hydroxyacetone, dihydroxyacetone,glycol aldehyde, dihydroxybutanone, 2,3-dihydroxyacrylaldehyde(triosereductone), ascorbic acid, cyclopentenediolone (reductic acid),ethyl oz-amino-B-ketobutyrate or a mixture of two or more of these isused as reducing agent in the presence of a quinoid compound which issoluble in water within the said pH range.

2. A process as claimed in claim 1 wherein at least l% by weight ofreductone and/or reductonate is used based on pure dye.

3. A process as claimed in claim 1 wherein from 0.1 to by weight ofquinoid compound is used based on reducing agent.

4. A process as claimed in claim 1 wherein from 2 to 5% by weight ofquinoid compound is used based on reducing agent.

5. A process as claimed in claim 1 wherein the process is carried out ata pH of l3 or more.

6. A process as claimed in claim 1 carried out at a temperature of fromroom temperature to about 100C.

7. A process for dyeing or printing cellulosic textiles with vat dyes ina pH range from about 12 upward wherein hydroxyacetone,dihydroxyacetone, glycol aldehyde, dihydroxybutanone,2,3-dihydroxyacrylaldehyde (triosereductone), ascorbic acid,cyclopentenediolone (reductic acid), ethyl a-amino-B-ketobutyrate or amixture of two or more of these is used as reducing agent in thepresence of a benzoquinone, a naphthoquinone, an anthraquinone or amixture thereof each of which bears one or more of the substituents:chlorine, amino, carboxyl and sulfonic acid, said quinoid compound beingsoluble in water in the said pH range.

8. A process for dyeing or printing cellulosic textiles as set forth inclaim 7 wherein hydroxyacetone, dihydroxyacetone, glycol aldehyde,dihydroxybutanone, 2,3-dihydroxyacrylaldehyde (trisereductone), ascorbicacid, cyclopentenediolone (reductic acid), ethyl a-amino-B-ketobutyrateor a mixture of two or more of these is used as reducing agent in thepresence of at least one quinoid compound selected from the groupconsisting of 2-hydroxyanthraquinone, 2,6-dihydroxyanthraquinone,2,7-dihydroxyanthraquinone, l,4-dihydroxyanthraquinone, anthraquinone-2-carboxylic acid, anthraquinone-Z-sulfonic acid,

anthraquinone-2,6-disulfonic acid, anthraquinone-Zfl disulfonic acid,l,4-diaminoanthraquinone-2-sulfonic acid, tetrachlorobenzoquinone and 1,4- naphthoquinone.

9. A composition of matter comprising a vat or sulfur dye which has beenmade ready for use by adjustment of the pH to about 12 or more, areducing agent selected from the group consisting of hydroxyacetone,dihydroxyacetone, glycol aldehyde, dihydroxybutanone,2,3-dihydroxyacrylaldehyde (triosereductone), ascorbic acid,cyclopentenediolone (reductic acid), ethyl a-amino-B-ketobutyrate or amixture of two or more of these and a quinoid compound as an acceleratorwhich is soluble in water at least within the said pH range.

10. A composition of matter as set forth in claim 9 in which saidreducing agent is selected from the group consisting of hydroxyacetone,dihydroxyacetone, glycol aldehyde, dihydroxybutanone,2,3-dihydroxyacrylaldehyde (triosereductone), ascorbic acid,cyclopentenediolone (reductic acid), ethyl a-amino-B- ketobutyrate or amixture of two or more of these and said quinoid compound is selectedfrom the group consisting of 2-hydroxyanthraquinone,2,6-dihydroxyanthraquinone, 2,7-dihydroxyanthraquinone,1,4-dihydroxyanthraquinone, anthraquinone-2-carboxylic acid,anthraquinone-2-sulfonic acid, anthraquinone-2,6- disulfonic acid,anthraquinone-Z,7-disulfonic acid, 1,4- diaminoanthraquinine-2-sulfonicacid, tetrachlorobenzoquinone and l,4-naphthoquinone.

ll. A process as set forth in claim 1 wherein hydroxyacetone is used asthe reducing agent.

12. A composition of matter as set forth in claim 9 wherein saidreducing agent is hydroxy acetone.

1. A PROCESS OF DYEING OR PRINTING CELLULOSE TEXTILES WITH VAT DYES IN APH RANGE FROM ABOUT 12 UPWARD WHEREIN HYDROXYACETONE, DIHYDROXYACETONE,GLYCOL ALDEHYDE, DIHYDROXYBUTABONE, 2,3-DIHYDROXYACRYLALDEHYDE(TRIOSEREDUCTONE), ASCORBIS ACID, CYCLOPENTENEDIOLONE (REDUCTIC ACID),ETHYL A-AMINOB-KETOBUTYRATE OR A MIXTURE OF TWO OR MORE OF THESE IS USEDAS REDUCING AGENT IN THE PRESENCE OF A QUINOID COMPOUND WHICH IS SOLUBLEIN WATER WITHIN THE SAID PH RANGE.
 2. A process as claimed in claim 1wherein at least 100% by weight of reductone and/or reductonate is usedbased on pure dye.
 3. A process as claimed in clAim 1 wherein from 0.1to 10% by weight of quinoid compound is used based on reducing agent. 4.A process as claimed in claim 1 wherein from 2 to 5% by weight ofquinoid compound is used based on reducing agent.
 5. A process asclaimed in claim 1 wherein the process is carried out at a pH of 13 ormore.
 6. A process as claimed in claim 1 carried out at a temperature offrom room temperature to about 100*C.
 7. A process for dyeing orprinting cellulosic textiles with vat dyes in a pH range from about 12upward wherein hydroxyacetone, dihydroxyacetone, glycol aldehyde,dihydroxybutanone, 2,3-dihydroxyacrylaldehyde (triosereductone),ascorbic acid, cyclopentenediolone (reductic acid), ethyl Alpha -amino-Beta -ketobutyrate or a mixture of two or more of these is used asreducing agent in the presence of a benzoquinone, a naphthoquinone, ananthraquinone or a mixture thereof each of which bears one or more ofthe substituents: chlorine, amino, carboxyl and sulfonic acid, saidquinoid compound being soluble in water in the said pH range.
 8. Aprocess for dyeing or printing cellulosic textiles as set forth in claim7 wherein hydroxyacetone, dihydroxyacetone, glycol aldehyde,dihydroxybutanone, 2,3-dihydroxyacrylaldehyde (trisereductone), ascorbicacid, cyclopentenediolone (reductic acid), ethyl Alpha -amino- Beta-ketobutyrate or a mixture of two or more of these is used as reducingagent in the presence of at least one quinoid compound selected from thegroup consisting of 2-hydroxyanthraquinone, 2,6-dihydroxyanthraquinone,2,7-dihydroxyanthraquinone, 1,4-dihydroxyanthraquinone,anthraquinone-2-carboxylic acid, anthraquinone-2-sulfonic acid,anthraquinone-2,6-disulfonic acid, anthraquinone-2,7-disulfonic acid,1,4-diaminoanthraquinone-2-sulfonic acid, tetrachlorobenzoquinone and1,4-naphthoquinone.
 9. A composition of matter comprising a vat orsulfur dye which has been made ready for use by adjustment of the pH toabout 12 or more, a reducing agent selected from the group consisting ofhydroxyacetone, dihydroxyacetone, glycol aldehyde, dihydroxybutanone,2,3-dihydroxyacrylaldehyde (triosereductone), ascorbic acid,cyclopentenediolone (reductic acid), ethyl Alpha -amino- Beta-ketobutyrate or a mixture of two or more of these and a quinoidcompound as an accelerator which is soluble in water at least within thesaid pH range.
 10. A composition of matter as set forth in claim 9 inwhich said reducing agent is selected from the group consisting ofhydroxyacetone, dihydroxyacetone, glycol aldehyde, dihydroxybutanone,2,3-dihydroxyacrylaldehyde (triosereductone), ascorbic acid,cyclopentenediolone (reductic acid), ethyl Alpha -amino- Beta-ketobutyrate or a mixture of two or more of these and said quinoidcompound is selected from the group consisting of2-hydroxyanthraquinone, 2,6-dihydroxyanthraquinone,2,7-dihydroxyanthraquinone, 1,4-dihydroxyanthraquinone,anthraquinone-2-carboxylic acid, anthraquinone-2-sulfonic acid,anthraquinone-2,6-disulfonic acid, anthraquinone-2,7-disulfonic acid,1,4-diaminoanthraquinine-2-sulfonic acid, tetrachlorobenzoquinone and1,4-naphthoquinone.
 11. A process as set forth in claim 1 whereinhydroxyacetone is used as the reducing agent.
 12. A composition ofmatter as set forth in claim 9 wherein said reducing agent is hydroxyacetone.